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    <title>Document</title>
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<body>
    <div class="jumbotron jumbotron-fluid">
        <div class="container text-center">
          <h1 class="display-4"> JavaScript ToDo</h1>
          <p class="lead">代办事项</p>
        </div>
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      <div class="container">
          <div class="row">
              <div class="col-12">
                <form class="mb-5" onsubmit="return false">
                    <div class="form-group">
                      <input id="ipt" type="text" class="form-control" placeholder="在此输入任务...">
                    </div>
                    <button  id="btn" type="submit" class="btn btn-primary btn-block">添加</button>
                  </form>
                  <ul class="list-group" id="ul"></ul>
              </div>
          </div>
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      <script src="script.js"></script>
</body>
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